For the wealthiest passengers--the ones who pioneered air travel in the first place--the aviation industry is researching high-speed civilian aircraft, which could be flying by 2030. These would cater to the free-spending uber-CEO as well as the adventure seeker, who might spend six figures for a ride.

The SpaceLiner, a hydrogen-powered rocket plane conceived by the German Space Agency, could someday carry up to 50 passengers through the upper atmosphere. Brussels to Sydney? A 90-minute hop. Virgin Galactic and others are proposing similar suborbital flights. Only the 10-minute launch would be powered. "The other 80 minutes is gliding, atmospheric flight," says Martin Sippel, the SpaceLiner's chief investigator. Top speed: Mach 20, nearly 24 times the cruising speed of a Boeing 787.